1. Field of the Invention
This invention relates to specifically modified copolymers derived from pivalolactone ##STR1## and isoprene and/or butadiene.
2. Description of the Prior Art
ABA type copolymers are taught in Sharkey, U.S. Pat. No. 3,557,255, wherein the A blocks are polypivalolactone and the B block is polyisoprene or polybutadiene. Copolymers taught herein are structurally different from such prior art copolymers in that they contain a ##STR2## unit between A and B blocks. Processes are nonanalogous.
The copolymers taught in Netherlands 70.03074 are distinguishable from those taught herein on the basis of obvious structural differences in the location of polypivalolactone segments along the backbone, or, on the type linkage by which the segments are attached, or, on the physical properties that characterize them, e.g., melt flow properties. The prior art process differs in several aspects including, inter alia: it begins with a preformed nonlithiated polymer that must first be dissolved; the dissolved polymer, if not intrinsically carboxylated, is carboxylated by reaction with a carboxylic acid or anhydride.